Diamond Grades

Most surface-set diamond bits manufactured by Dimatec are available with one of three standard grades of natural drill diamond set on the cutting surfaces of the bit face. The diamond grades are described as follows:

AA Grade

High quality natural drill diamond. These stones are mainly round with a small percentage of octahedral, dodecahedral and off-shaped stones.

P2 Grade

Medium quality mechanically processed (rounded) diamond. These stones have a high lustre to satin finish with a varying degree of color with no greens, blacks or dark yellows. Although these diamonds are fully processed, the surface texture of these stones may exhibit some irregularities but are free of any fissures and cracks.


These stones are sometimes referred to as “black diamond” and are an opaque, gray/black cryptocrystalline aggregate of diamond crystals, graphite and amorphous carbon. Carbonados usually occur as relatively large, irregular shaped crystalline structures that are mechanically split into angular shapes and desired sizes. Normally, individual carbonado crystals are sized in the range of 10 stones per carat (SPC) or larger. Bits set with carbonados are particularly well suited for use in drilling softer formations or hard/soft blended formations such as serpentine.

Physical Properties of Natural Diamond Grades

Application of Natural Diamond Grades

The general rule for selecting the appropriate diamond grade is that the harder the rock, the better the diamond toughness and crystal geometry should be. For example, the selection of the “AA” grade would be appropriate for use in a consolidated, hard limestone formation while the selection of the “P2” grade would be appropriate for use in a soft schist formation.